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Toyota Sienna Heating / Cooling



  • Well, we don't have a "common" setting other than when a "synch" button that sets the rear and two front air controls (L/R) to the same temperature. I just confirmed that the drivers side heat blows cold on the synch setting as well.

    So if the driver's side solar radiation sensor has failed, is this something that I could purchase and change or am I subject to working with the dealer on this? I am out of warranty and irritated that when we took it to the dealer during the warranty pointing out the sound, they said they couldn't reproduce it.

    I appreciate your advice!
  • stephrstephr Posts: 2
    I've taken my 2006 Sienna in 3 times in a month because I can't control the rear temp from the front. I can only control the fan speed. I have less than 20K miles, and have never had this issue before now. Any one had similar issues? The only way I can control the rear temp is to get in the back and adjust the control.
  • stephrstephr Posts: 2
    Disregard - my dealership tells me that's how it works.....
  • On my 2006 XLE Sienna the air coming from the front air vents remains hot until you switch the temperature down to lowest temperature. Once you set it to low, the A/C will run you out of the van. It you then bump the temperature up one notch, to 65, the air will turn hot again (while on A/C). This happens on both the drivers and passengers side of the van. I haven't checked the rear climate controls to see what happens in the back. This first happened while we were in Texas for Christmas and were going to take the van to dealership down their but it started working again. I figured it wouldn't be worth our time if it's working because they wouldn't be able to identify this issue. The issue has once again pop up it ugly head and our local dealership has being looking at for a day with on good solution. I'm just curious it anybody else has experience this type of issue and if so, what was one to resolve it. Thanks!
  • wwestwwest Posts: 10,706
    You have an open temperature sensor. One of those is the cabin temperatrue sensor just behind that vane window above the driver's right knee. If that is open the control system will sense that the cabin is extremely COLD, regardless of actual, and run the system in heating mode constantly.

    The other possibility, although less likely, would be the OAT sensor being open and the system thinkng that the outside world is extremely cold. If you have an outside temperature indicator you can verify the OAT sensor that way.

    The OAT sensor is usually mounted behind the front bumber but in front of the radiator/condensor stack.
  • Our local dealership spent a complete day looking our van and they now believe they've identified the problem. They said that the cabin temperature sensor was bad and needed replaced. The part is on order and we'll see if this resolve this issue. Thanks, I appreciate your response!
  • mafaustmafaust Posts: 1
    Hi, the rear heat in my Sienna will only blow cold air. I have the manual control system, not the automatic air temp system. With the front fan speed selector on REAR, meaning all the rear system should be controlled by the rear control panel, and the rear temperature selector set to hot and the air flow selector on any of the three choices, I get cold air out of all the upper and lower vents.

    Has anyone else experienced this or does anyone have any ideas as to what is going on/how to address it?

  • shodougshodoug Posts: 1
    The blower motor for the rear AC will not work.

    Since the rear heater blower works fine, I am thinking that the resistor is OK.

    It has been a while since I looked at the wiring diagram, but I remember that there was a relay that selected the ac or the heat blower for the rear. Does anyone know where this relay is located? The diagram did not give out that information.

    I am figuring that it is either the relay, wiring to the blower motor, or the blower motor itself. Are there any other things I should be considering?

    Now that spring is coming, it would be nice to get the ac working everywhere. :)

  • jzx81jzx81 Posts: 3
    I have a 2005 Toyota Sienna with roughly 9k miles on it and the A/C died completely while taking the mom out for Mother's Day yesterday. To make matters worse, the warranty ended two weeks ago and I did not get it extended. The A/C button does not light up when pressed and the blower does not come on at any blower setting level. My mechanic friend said the blower is still getting power when activated by the switch. He suspects the resistor pack is bad that is located close to the blower motor. I had no A/C problems prior to this or any signs leading up to this failure. Anyone have any experience with this problem before or suggestions? Thank you for any input!
  • jzx81jzx81 Posts: 3
  • jijubarjijubar Posts: 1
    I too have a similar problem. The compressor clutch does not always engage when AC is turned on but when it does, everything works great. Where exactly is the cabin temp sensor and if open, can it be substituted with a resistor of appropriate value to indicate the need for cold air?
  • 19791979 Posts: 2
    We have a 04 Senna with about 56000 miles on it. When the engine is on it sounds like water running in the air conditioning heating unit. Does anybody have any ideas? The dealer says he can hear it but will need the car at least a day and will have to contact tech support.
  • wwestwwest Posts: 10,706
    There is ALWAYS water/coolant running through the heater core within the A/C plenum but you should never hear it unless the coolant level is low enough to be moving air bubbles.

    Be sure your coolant level is proper.
  • pit1pit1 Posts: 7
    :( :cry: We have 20004 Senna with 25,0000 miles. Last week the rear ac stopped blowing cold air. The front is working ok. I open the rear compartment where the rear blower is located and feels like there is plenty of cold air inside the blower. Its just not getting to the rear vents. Can anyone help/ thanks
  • brintegrabrintegra Posts: 2
    hi there!

    did u get this problem sorted out - was it the resistor or fuse / i have a sienna with 10K miles with the exact problem.

    would appreciate any inputs - my email is [email protected]

  • jzx81jzx81 Posts: 3
    It turned out to be the A/C Heater Relay, PN 90080-87025, $16.40 from dealer. Luckily, we have a guy at the dealership (bought the Sienna from him) that hooked us up with free service even though warranty was over.
  • 19791979 Posts: 2
    Didn't get it fixed. Dealer wanted $1100 To replace the ac panel and wasn't sure that would fix it. We just live with it doesn't do it all the time.
  • relooky01relooky01 Posts: 6
    I also have a 2005 Sienna. On several occasions the blower and AC would not come on when the blower switch is in any of the ON positions. They did eventually come on and worked properly the rest of the day. I suspect the HTR relay (Toyota PN 90080-87025) is working intermittently and have a new one on order ($18.18 from the local Toyota dealer). It is located in the fuse box under the hood next to the battery. I switched this relay with the RR A/C relay next to it and then the rear heater/AC blower would not come on but the front blower worked fine.
  • khardingkharding Posts: 5
    I am having the exact same problem with my heater/cooling fan switch. I start up the car, try to turn on the A/C or Heater, and nothing works. I then drive for about 5-10 minutes, with the setting on low and it may kick on. I try to turn the A/C to a higher setting and it goes off. Did replacing the HTR relay ultimately fix the issue? $18.18 is a little more palatable than replacing the switch, and easier also...
  • relooky01relooky01 Posts: 6
    I replaced the HTR relay on Saturday and so far the blower is working fine. Once the blower came on I did not have a problem with the A/C going off at a higher speed setting as you mentioned. Once it came on it worked just fine at all speeds. By the way, I was able to remove the cover from the old relay by prying it over the 4 tabs. I connected the relay to a 12 volt power supply and measured the resistance across the closed contacts (the two large terminals on the relay). The resistance varied each time I energized the relay. I then polished the contacts with some real fine crocus cloth followed by a strip of heavy paper (from a business card). The resistance across the contacts was essentially zero after that with the relay energized and the relay worked fine. Although I did not try it back in the car I have every reason to believe it would work as good as new. As a suggestion, try swapping the HTR and the RR A/C relays (they are located next to each other) and see if the intermittent problem moves to the rear heater blower. Good luck!
  • We have the same problem in our '06 Sienna. We brought it to the dealership, but they couldn't figure out what was wrong - we should have checked this forum first. How do you remove the HTR relay? If you just pull hard enough, will the relay pop off? Do you need to pry the relay off with a tool? Do you remove the blue cover? Thanks.
  • khardingkharding Posts: 5
    To remove the HTR relay, you open up the fuse box under the hood near the driver's side, pop off the fuse box cover and then find the appropriate relay. On my '05, the schematic is on the under side of the fuse box cover. You should just pull the relay straight out like a fuse. I would avoid using a tool if at all possible so as not to break anything unless there is a special relay puller tool. The relay is in there tight, but with minimal wiggling, it should pop straight out. These relays cost about $18-20. I just switched out the RR A/C with the HTR relay and now we are dealing with the intermittent issue in the rear air. I will pick up another when convenient, but at least I know that this was the problem. I do not think the blue cover on the relay itself is removable. Good luck
  • xavyxavy Posts: 2
    Just purchased used 05 Sienna (50K) two months ago, wife noticed odorless vapor/smoke blowing out of center dash vent today. Has anyone ever encounter this before? What is the cause? Dealer wants us to bring in because they say they have never seen or heard of this issue.
    Are they just blowing smoke?
  • xavyxavy Posts: 2
    I purchased an OEM key today, and had locksmith cut key, no problem.
    Went to program myself, followed instruction, did not work. Any suggestions other than paying dealer $89.00 an hour for a 2 min. job? Thieves is the common word for them.
  • wwestwwest Posts: 10,706

    Humid day, A/C cools the air to dewpoint, you get FOG flowing out of the vents. Usually only lasts until the A/C is able to fully cool the evaporator down.
  • marty08marty08 Posts: 3
    I bought the Sienna in the Fall and when Winter came, we noticed that it takes over 20 minutes to get any considerable heat from the vents. If you let the vehicle in "Park", warming it up, it takes over 25 minutes to get any heat. When you drive it, within a minute of start-up, it is usually 20 minutes or 7 miles, before you get any heat. I've taken it into the dealership, under warranty and they stick the radiator and say it's OK. I tried to make them keep it overnight and start it in the morning, when it's cold and they claim that if it's at the correct operating temperature when they check it, it won't make a difference. I tried to explain that perhaps the thermostat is not closing all the way and the dealership stated that they have never heard of this. Has anyone else had this problem? I have a 97 4-Runner and a 90 Toyota Pick-up and both warm up within a few minutes and even the temperature guage goes to normal, just warming it up without driving it. :confuse:
  • wwestwwest Posts: 10,706
    Does the engine coolant temperature guage come up to the correct level in the normal time and yet there is no heat..??

    Or does the engine coolant not come up to temperature..??
  • mfc3mfc3 Posts: 8
    I have 2005 Sienna with only 10K miles. Now I press AC on/off switch and nothing happens. The AC switch light is always off. The air blows do work but they are just sucking air from outside. Does anyone know what is going on ? Where should I look for ? The car warranty just expired.
  • I had a similar issue with the switch in the on position, no A/C light, and no fan was functioning. I switched out the A/C relay in the fuse box and that seemed to fix it. I have not dealt with a fan that is working but A/C not working. Sorry.
  • mfc3mfc3 Posts: 8
    Thanks, kharding. I will go back to check if the fan is actually working. I did recall the rear AC fan is woring. Do they(rear and front AC) share the same relay ?
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